Recovery of Fine and Ultrafine Mineral Particles by Electroflotation – A Review

Fine and ultrafine particles are successfully recovered by flotation when fine bubbles are present. Electroflotation is a technique in which fine bubbles are generated by the electrolysis of water. This article reviews the experimental studies into mineral recovery by electroflotation and the potential application of electrolytic bubbles in the recovery of fine and ultrafine mineral particles. The literature reveals that electroflotation resulted in better recoveries of ultrafine particles (e.g. dolomite, magnesite, and pyrite) as compared with dispersed-air flotation because electrolytic bubbles are smaller in size and are more active than those generated during dispersed-air flotation.     

Efficacy of Silicosec, filter cake and wood ash against the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) on three maize genotypes

The effectiveness of the diatomaceous earth Silicosec, a mineral industrial filter cake and domestic wood ash, applied at three different rates for the control of the maize weevil, Sitophilus zeamais, on three maize genotypes was determined. Treatment with Silicosec was the most effective followed by filter cake and wood ash. The treatments reduced progeny emergence, percentage grain damage and grain weight losses, but did not affect percentage seed germination. Grain treated with wood ash at all rates resulted in a relatively low mortality 3 days after infestation as compared to other treatments. However, all treatments caused high mortality (97-100%) after 15 days of exposure. Therefore, Silicosec, filter cake and wood ash can be considered as potential components of an integrated pest management strategy against the maize weevil.     

Wrap‐around electrodes for microLED tiled displays

The authors have developed a process to create wrap‐around electrodes (WAEs) on glass for use in tiled microLED display applications. The electrodes have small size and spacing, low resistance, and good reliability. In addition, an opaque overcoat protects the edges of the tiles and reduces seam visibility. These electrodes allow bezel‐free tiled operation for high‐resolution displays.     

AEB系统的CarMaker/Simulink联合仿真研究

针对汽车AEB系统,提出了一种基于碰撞时间的控制算法.研究选取车辆碰撞时间作为控制变量,通过输出的期望减速度来确定各车轮上的制动力矩,从而提高车辆的纵向行驶安全性.为保证研究的准确性,采用CarMaker/Simulink联合建立虚拟仿真环境,并选取C-NCAP(2018版)AEB系统的追尾评分场景进行验证.结果 表明:试验较好地验证了AEB系统算法的有效性;根据碰撞时间可以准确预判危险程度,使车辆保持在合适的安全车距范围内.     

Neural networks for prediction of deflection in composite bridges

Neural networks have been developed for prediction of deflections, at service load, in steel-concrete composite bridges incorporating flexibility of shear connectors, shear lag effect and cracking in concrete slabs. Three neural networks have been presented to cover simply supported bridges, two span continuous bridges and three span continuous bridges. The use of the neural networks requires a computational effort almost equal to that required for the simple beam analysis (neglecting flexibility of shear connectors, shear lag effect and cracking of concrete). The training and testing data for neural networks are generated using finite element software ABAQUS. The neural networks have been validated for number of bridges and the errors are found to be small. Closed form solutions are also proposed based on the developed neural networks. The networks/ closed form solutions can be used for rapid prediction of deflection for everyday design.     

Design of reduced complexity feedback precoding for MIMO‐OFDM

Beamforming technique is applied to significantly increase the performance of a MIMO system, if the channel information (CI) of the communication system is available at the transmitter. For the transmitter to obtain the entire CI, however, a considerable reverse‐link bandwidth is required. To save the bandwidth, a limited‐rate closed‐loop system, therefore, uses a predetermined codebook which is derived from the CI. The codebook consists of a finite number of precoders out of which the index of the best one is transmitted from the receiver to the transmitter using only a few bits saving substantial bandwidth. However, the amount of bits that need to be fed back can still be significantly large for MIMO‐OFDM systems when the precoding matrix index (PMI) for each subcarrier should be transmitted. Such per‐subcarrier precoding scheme has high feedback overhead and also incurs huge computational cost to determine the best PMI for each subcarrier. We, therefore, propose a per‐band precoding scheme that precodes a band (group) of subcarriers by only one precoder. More importantly, we develop, for the proposed per‐band scheme, reduced‐complexity precoding selection methods that lead to the design of efficient receivers. The effectiveness of the proposed scheme is investigated through computer simulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Separation of Radioactive Elements from Ethiopian Kenticha Pegmatite Ore by Hydrometallurgical Methods

The leaching and extraction behavior of uranium and thorium from a high-grade Ethiopian pegmatite ore in a mixture of hydrofluoric acid and sulfuric acid has been investigated. The effects of variables such as the temperature, particle size, acid concentration, and leaching time were studied. The leaching efficiency of uranium increased with increasing temperature to 150°C, at which 96% removal of uranium was achieved. Particles in the size range of ??100?+?75 μm resulted in the highest leaching of uranium, while formation of a colloidal suspension was observed when using a fine particle size fraction (??75 μm). The dissolution of uranium increased with increasing leaching time. No significant systematic dependence of the leachability of thorium on the above variables was observed. Optimum extraction of uranium and thorium using D₂EHPA was obtained when using aqueous/organic phase volume ratio of 1:1, solvent concentration of 0.3 M, and contact time of 20 min.     

Camber Evolution and Stress Development of Porous Ceramic Bilayers During Co‐Firing

Camber evolution and stress development during co‐firing of asymmetric bilayer laminates, consisting of porous Ce_0.9Gd_0.1O_1.95 gadolinium‐doped cerium oxide (CGO) and La_0.85Sr_0.15MnO₃ lanthanum strontium manganate (LSM)‐CGO were investigated. Individual layer shrinkage was measured by optical dilatometer, and the uniaxial viscosities were determined as a function of layer density using a vertical sintering approach. The camber evolution in the bilayer laminates was recorded in situ during co‐firing and it was found to correspond well with the one predicted by the theoretical model. The estimated sintering mismatch stress in co‐fired CGO‐LSM/CGO bilayer laminates was significantly lower than general sintering stresses expected for free sintering conditions. As a result, no co‐firing defects were observed in the bilayer laminates, illustrating an acceptable sintering compatibility of the ceramic layers.     

Characterization of honeys by their botanical and geographical origins based on physico-chemical properties and chemo-metrics analysis

Honey, because of its nutritional and medicinal values, is in high demand and has become one of the important commodities. However, the issue of its quality and authenticity remain as important factors in consumption and marketing of honey. To assess the possibility of discriminating honeys by their geographical and botanical origins; 30 fresh honey samples of different botanical and geographical origins were collected and their major physico-chemical properties such as: total dissolved sugar (TDS), total ash, sugar profile, acidity, metallic ions and electric conductivity (EC) were investigated. The data was subjected to different chemo-metric (Hierarchical Cluster, Principal components and stepwise discriminant) analysis. Among the 23 characters used in the analysis; only 11 (TDS, EC, acidity, total ash, colour, and some specific metallic ions) characters have showed significant variations among different origin honeys. According to the stepwise discriminant analysis; 11 variables confirmed the grouping of the honey samples into four cluster groups based on their botanical and geographical origins. The clustering of the honeys associated with dominant plant source & climatic conditions of their origins. The study generally revealed the successful discrimination of honeys into their botanical and geographical provenances using fewer physico-chemical characters supported with melissopalynological data through applying suitable chemo-metric analysis.     

Low temperature sintering of (Ba0.85Ca0.15) (Ti0.90Zr0.10)O3 lead-free piezoceramic with the additive of MnO2

Lead-free (Ba_0.85Ca_0.15) (Ti_0.90Zr_0.10)O₃ (15/10 BCZT) piezoelectric ceramics were prepared by a standard solid solution and sintered at different temperature of 1300 °C and 1500 °C at a time. The 15/10BCZT piezoceramics were prepared at 1300 °C sintering temperature by doping different amount of MnO₂.The ceramics show a phase transition from a freoelectric tetragonal phase to a rhombohedral and tetragonal ferroelctric phase and to a single rhombohedral phase with increasing MnO₂ content. The addition of MnO₂ significantly improves the sinterbility of the 15/10BCZT piezoceramics, and reducing the sintering temperature from 1500 °C to 1300 °C by 200 °C but showing comparable piezoelectric properties. With 0.4 mol% of the dopant, ～96.5% of the theoretical density of the ceramics was achieved with excellent piezoelectric coefficient d₃₃ ~ 534pC/N, which is nearly equal to the value obtained from the ceramics sintered at 1500 °C which has a piezoelectric coefficient d₃₃ ~ 570pC/N, high density (~ 5.59 g/cm³), maximum remnant polarization (P_r = 24 μC/cm²), relatively large grain size (10.4 μm) and the least coercieve field (E_c = 0.42 kV/mm). However, a high concentration of MnO₂ deterioated the properties of the ceramics because of increasing of oxygen vacancies and associated defects. The results indicate that the BCTZ-y mol% MnO₂ ceramics are one of the promising lead-free piezoelectric candidates for high temperature applications.